square wave generator

[FvM]

Yes. Do you think, it's available from stock with 500 MHz?

 

[keith1200rs]

I am now a bit lost as to what i should do. Is it possible to directly design a 500 Mhz square wave oscillator stable to 10ps or do i have to design a sine wave first and then put it into a PLL synthesizer to get the stablility from the crystal oscillator? Does this mean that i must design a Clapp,wein bridge etc. oscillator(bec i cant find equations and circuits that help me design this from scratch, the bias circuits and the colpitts are always seperate, how do i combine them)? using s-parameters and such? I have tried some square wave circuits i found on the web, but they don't work to well at certain frequencies-something tells me that each circuits have limitations to the frequency they can produce.

How can i understand the fundamentals of electronics/electronic components in order to build my own square wave generator? I am in urgent need of help, this must be done, and fast - PLS HELP!!

Have you rejected the idea of chips like the ICS525? I thought that would directly do the job all in one chip. I guess I have missed something.

Keith.

 

[karesz]

Yes, seems you can have it (version: PECL, 2,5V) from Newark for $20.11...
**broken link removed**

 

[FvM]

Have you rejected the idea of chips like the ICS525?

I think, the 10 ps jitter specification is clearly against it. That's the really annoying point in my opinion, you and others have
made valuable suggestions, that could be targeted much more precisely with a clear specification.

 

[Janelda]

Hi all,

I have not rejected anybodies ideas, im sorry that i havent mentioned my concerns with your suggestions. The following is what i saw:

The ICS525-01 says that it can get output frequencies of up to 160 Mhz and the ICS525-02 says it gets up to 250 Mhz. I need 500 Mhz, so i thought that i can't use it.

When i looked at the Epson oscillators datasheet, it said saw oscillator, i need pulses, not saw waves.
Let me clear my requirements:

I must be able to select a period and pulse width using a computer. I just thought it would be a good start to first do the period selection and then worry about the pulse width selection. The period must be able to be adjusted from 50ns in steps of 2ns up until 500ns, meaning from 2 Mhz - 20 Mhz. the pulse widths must be adjustable in steps of 1ns, from 5ns until 80ns. I must also be able to delay the signal which i am not so concerned about right now as i can use a delay IC for that.

This project will be used to switch switches in radar-cross section antenna measurements, hence the high speed. The switches can be switched by either TTL or ECL levels.

This may not be a beginers project, but i am in desperate need of help of how to think, approach this and where to look that i am trying anything at this moment in time.

waiting to hear from you asap.

Added after 1 minutes:

oh, and the way i understand it is, the pulses must be stable to 10ps. i don't know how else to explain this.

 

[keith1200rs]

Hi all,

The ICS525-01 says that it can get output frequencies of up to 160 Mhz and the ICS525-02 says it gets up to 250 Mhz. I need 500 Mhz, so i thought that i can't use it.

But you actually only want 20MHz maximum. The ICS525 is a programmable synthesizer which can probably generate all the frequencies you want directly. However, as pointed out by FvM, the jitter of the ICS525 PLL is more than 10ps, so I suspect you are stuck with the idea of dividing down a 500MHz clock. As karesz said "not a beginner project"!

Keith.

 

[Janelda]

Yes i guess i am stuck with that idea, i thought it was a good idea to generate a sine wave and use an oscillator to stabalize it using the PLL synthesizer.

 

[FvM]

At the beginning it sounds like an (almost) simple square wave generator with digital programmable frequency. Adding programmable
pulse width and delay (related to what?), it becomes a complex digital design with now 1 ns time base and a challenging jitter specification.

Hopefully, the delay feature doesn't reveal as a high precision external trigger, which could upset possible design ideas once more...

Without the jitter specification, it would be a nice FPGA with PLL time base project. Now, at least low jitter high frequency clock source
is required, e.g. the said 500 MHz SAW oscillator. It could achieve 1 ns resolution utilizing double data rate techniques.

 

[Janelda]

Does anyone by any chance know if there exsists a programmable switch which one can set the open/close times? one which can switch in like 1ns? is there something like this